A third explosion was heard about two hours later, but there were no immediate details on the location or cause.
The first explosion occurred about 9:40 a.m. local time (1:40 a.m. EST) in the al-Jihad (search) district on the road leading to Baghdad's airport, about seven miles southwest of the U.S.-led occupation authority's headquarters.
A second roadside bomb went off on the highway in the al-Adil district, witnesses said. It was unclear if there were any injuries.
Both roads are used regularly by coalition troops.